A typical storage/transport box has a tray-like floor having outer edges from which extend vertical wall panels. For maximum rigidity, it is standard to make the floor of a pair of welded-together profiled panels made by injection molding. The floor is formed with an array of vertically throughgoing normally cylindrical holes that pass through both panels, that is that each has an upper part in the upper floor panel and a lower part in the lower floor panel.
An automated unloader has pushers that can move up through these holes to raise objects held in the box so they can be engaged by a rake-type grab and transported away. Such containers can be collapsible and formed as so-called pallet boxes, and are used both to transport objects and to store them on shelves.
Such a double-floor box is shown, for example in DE 196 27 887 and EP 0 621 190.
The floor of such a box, which in fact can be used all alone as a tray, is typically made by so-called vibration welding. To do this the lower panel is held and the upper panel is pressed down against it and vibrated. The friction at the interface between the panels melts the plastic and, when stopped, the panels fuse together at the fused film of plastic created where they contact each other. Once the fused film cools the two panels are drilled or milled to form the vertical holes through them, a wholly separate production step.
As a result holes have sharp edges are created both on the upper face of the floor and on the lower face at the outer periphery of the openings. In fact burrs are often formed that can, first of all, damage the load or the deposited items, and second, prevent the frictionless and smooth conveyance of the transport means on a conveyor belt or roll-type conveyor track.
In addition, when the openings are cut, plastic shavings are inevitably created that can both fall into the conveyor system and also be deposited on the load-bearing upper surface in the transport container. Removal of the plastic shavings is also in particular impeded by their static charge.
Subsequent machining of the cut openings by a further cutting and grinding procedure to round their edges requires an expensive additional operation, as a result of which the production process is lengthened to a not insignificant extent.